Methods of reducing the amount of colorant in a multilayer film

ABSTRACT

The present disclosure is directed to methods of reducing the amount of colorant in a multilayer film and achieving an L* color less than 30 and a 60 degree gloss value less than 10. The multilayer film has a first polyimide layer and a second polyimide layer containing a matting agent, submicron carbon black and submicron fumed metal oxide.

FIELD OF DISCLOSURE

This disclosure relates generally to a method of reducing the amount ofcolorant in a multilayer film. More specifically, the multilayer filmhas a first polyimide layer and a second polyimide layer containing amatting agent, submicron carbon black and submicron fumed metal oxide.

BACKGROUND OF THE DISCLOSURE

Industry increasingly desires polyimide films for electronic applicationto be matte in appearance, have a specific color, durability to handlingand circuit processing, and when used as a coverlay, provide securityagainst unwanted visual inspection of the electronic componentsprotected by the coverlay. Single layer matte luster films do not havean L* color less than 30 providing deep, rich saturated colors desiredby industry. Typically, as the amount of matting agent is increased thecolor of the film becomes muted. The effect of increased surfaceroughness from the matting agent is the dilution of the pigment color sothat it appears lighter and less saturated. This is caused by thedilution of the diffuse reflectance (where pigment color is perceived)by the increased scatter of the specular reflectance (white light). Therougher the surface, the lower the gloss and greater the scatter of thespecular reflectance. Thus, as gloss decreases, L* (lightness) typicallyincreases. Adding more colorant does not decrease the L* color. Thus,simultaneously achieving low gloss and low L* color is thereforedifficult.

For the forgoing reasons, a need exists for a polyimide film that ismatte in appearance, has deep, rich saturated colors, as well as providesufficient optical density to provide visual security when used as acoverlay while having acceptable electrical properties (e.g., dielectricstrength) mechanical properties, and durability to handling and circuitprocessing.

SUMMARY

The present disclosure is directed to methods of reducing the amount ofcolorant in a multilayer film and achieving an L* color less than 30 anda 60 degree gloss value less than 10. The multilayer film has a firstpolyimide layer and a second polyimide layer containing a matting agent,submicron carbon black and submicron fumed metal oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an adhesive layer in direct contact with the firstpolyimide layer opposite from the second polyimide layer according toone embodiment of the present disclosure.

FIG. 2 illustrates a third polyimide layer, an adhesive layer in directcontact with the second polyimide layer on a surface of the secondpolyimide layer furthest from the first polyimide layer according to oneembodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to methods of reducing the amount ofcolorant in a multilayer film and achieving an L* color less than 30 anda 60 degree gloss value less than 10. The multilayer film has a firstpolyimide layer and a second polyimide layer containing a matting agent,submicron carbon black and submicron fumed metal oxide.

The use of the “a” or “an” are employed to describe elements andcomponents of the invention. This is done merely for convenience and togive a general sense of the invention. This description should be readto include one or at least one and the singular also includes the pluralunless it is obvious that it is meant otherwise.

The term “polyamic acid” as used herein is intended to include anypolyimide precursor material derived from a combination of dianhydrideand diamine and capable of conversion to a polyimide.

First Polyimide Layer

The first polyimide layer is derived from at least 50 mole percent of anaromatic dianhydride, based upon a total dianhydride content of thepolyimide, and at least 50 mole percent of an aromatic diamine basedupon a total diamine content of the polyimide. The term “dianhydride” asused herein is intended to include precursors, derivatives or analogsthereof, which may not technically be a dianhydride but wouldnevertheless react with a diamine to form a polyamic acid which could inturn be converted into a polyimide. The term “diamine” as used herein isintended to include precursors, derivatives or analogs thereof, whichmay not technically be a diamine but would nevertheless react with adianhydride to form a polyamic acid which could in turn be convertedinto a polyimide.

In one embodiment, the aromatic dianhydride is selected from the groupconsisting of:

-   pyromellitic dianhydride;-   3,3′,4,4′-biphenyl tetracarboxylic dianhydride;-   3,3′,4,4′-benzophenone tetracarboxylic dianhydride;-   4,4′-oxydiphthalic anhydride;-   3,3′,4,4′-diphenyl sulfone tetracarboxylic dianhydride;-   2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane;-   Bisphenol A dianhydride; and-   mixtures and derivatives thereof.    In another embodiment, the aromatic dianhydride is selected from the    group consisting of:-   2,3,6,7-naphthalene tetracarboxylic dianhydride;-   1,2,5,6-naphthalene tetracarboxylic dianhydride;-   2,2′,3,3′-biphenyl tetracarboxylic dianhydride;-   2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;-   bis(3,4-dicarboxyphenyl) sulfone dianhydride;-   3,4,9,10-perylene tetracarboxylic dianhydride;-   1,1-bis(2,3-dicarboxyphenyl) ethane dianhydride;-   1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride;-   bis(2,3-dicarboxyphenyl) methane dianhydride;-   bis(3,4-dicarboxyphenyl) methane dianhydride;-   oxydiphthalic dianhydride;-   bis(3,4-dicarboxyphenyl) sulfone dianhydride;-   mixtures and derivatives thereof.    In some embodiments, examples of suitable aliphatic dianhydrides    include but are not limited to: cyclobutane dianhydride;    [1S*,5R*,6S*]-3-oxabicyclo[3.2.1]octane-2,4-dione-6-spiro-3-(tetrahydrofuran-2,5-dione);    and mixtures thereof.

In some embodiments, the aromatic diamine is selected from the groupconsisting of: 3,4′-oxydianiline; 1,3-bis-(4-aminophenoxy) benzene;4,4′-oxydianiline; paraphenylenediamine; 1,3-diaminobenzene;2,2′-bis(trifluoromethyl) benzidene; 4,4′-diaminobiphenyl;4,4′-diaminodiphenyl sulfide; 9,9′-bis(4-amino)fluorine; mixtures andderivatives thereof.

In another embodiment, the aromatic diamine is selected from a groupconsisting of: 4,4′-diaminodiphenyl propane; 4,4′-diamino diphenylmethane; benzidine; 3,3′-dichlorobenzidine; 3,3′-diamino diphenylsulfone; 4,4′-diamino diphenyl sulfone; 1,5-diamino naphthalene;4,4′-diamino diphenyl diethylsilane; 4,4′-diamino diphenysilane;4,4′-diamino diphenyl ethyl phosphine oxide; 4,4′-diamino diphenylN-methyl amine; 4,4′-diamino diphenyl N-phenyl amine; 1,4-diaminobenzene(paraphenylenediamine); 1,2-diaminobenzene; mixtures and derivativesthereof.

In some embodiments, examples of suitable aliphatic diamines include:hexamethylene diamine, dodecane diamine, cyclohexane diamine andmixtures thereof.

In one embodiment, the first polyimide layer comprises a polyimidederived from pyromellitic dianhydride and 4,4′-oxydianiline.

In some embodiments, the first polyimide layer is between and includingany two of the following thicknesses: 8, 10, 20, 30, 40, 50, 60, 70, 80,90, 100, 110, 120 and 130 microns thick. In another embodiment, thefirst polyimide layer is from 8 to 130 microns thick. In anotherembodiment, the first polyimide layer is from 10 to 30 microns thick. Inanother embodiment, the first polyimide layer is from 12 to 25 micronsthick.

The first polyimide layer may optionally contain 1 to 15 wt % lowconductivity carbon black. In some embodiments the first polyimide layercontains between and including any two of the following: 1, 5, 10 and 15wt % low conductivity carbon black. In yet another embodiment, the firstpolyimide layer contains 2 to 9 wt % low conductivity carbon black.

Low conductivity carbon black is intended to mean, channel type black,furnace black or lamp black. In some embodiments, the low conductivitycarbon black is a surface oxidized carbon black. One method forassessing the extent of surface oxidation (of the carbon black) is tomeasure the carbon black's volatile content. The volatile content can bemeasured by calculating weight loss when calcined at 950° C. for 7minutes. Generally speaking, a highly surface oxidized carbon black(high volatile content) can be readily dispersed into a polyamic acidsolution (polyimide precursor), which in turn can be imidized into a(well dispersed) filled polyimide base polymer of the presentdisclosure. It is thought that if the carbon black particles(aggregates) are not in contact with each other, then electrontunneling, electron hopping or other electron flow mechanism aregenerally suppressed, resulting in lower electrical conductivity. Insome embodiments, the low conductivity carbon black has a volatilecontent greater than or equal to 1%. In some embodiments, the lowconductivity carbon black has a volatile content greater than or equalto 5, 9, or 13%. In some embodiments, furnace black may be surfacetreated to increase the volatile content. Typically, a low conductivitycarbon black has a pH less than 6.

A uniform dispersion of isolated, low conductivity carbon blackparticles (aggregates) not only decreases the electrical conductivity,but additionally tends to produce uniform color intensity. In someembodiments the low conductivity carbon black is milled. In someembodiments, the mean particle size of the low conductivity carbon blackis between (and optionally including) any two of the following sizes:0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 microns.

The first polyimide layer may optionally contain 1 to 40 wt % pigment ordye. In some embodiments the first polyimide layer contains 1 to 40 wt %of a mixture of pigments and dyes. In some embodiments, the firstpolyimide layer contains between and including any two of the following:1, 5, 10, 15, 20, 25, 30, 35 and 40 wt % pigment, dye or mixturesthereof. In some embodiments, the first polyimide layer contains 1 to 40wt % of a mixture of at least two of the following: low conductivitycarbon black, pigments or dyes.

Virtually any pigment (or combination of pigments) can be used in theperformance of the present invention. In some embodiments, usefulpigments include but are not limited to the following: Barium LemonYellow, Cadmium Yellow Lemon, Cadmium Yellow Lemon, Cadmium YellowLight, Cadmium Yellow Middle, Cadmium Yellow Orange, Scarlet Lake,Cadmium Red, Cadmium Vermilion, Alizarin Crimson, Permanent Magenta, VanDyke brown, Raw Umber Greenish, or Burnt Umber. In some embodiments,useful black pigments include: cobalt oxide, Fe—Mn—Bi black, Fe—Mn oxidespinel black, (Fe,Mn)2O3 black, copper chromite black spinel, lampblack,bone black, bone ash, bone char, hematite, black iron oxide, micaceousiron oxide, black complex inorganic color pigments (CICP),(Ni,Mn,Co)(Cr,Fe)2O4 black, Aniline black, Perylene black, Anthraquinoneblack, Chromium Green-Black Hematite, Chrome Iron Oxide, Pigment Green17, Pigment Black 26, Pigment Black 27, Pigment Black 28, Pigment Brown29, Pigment Brown 35, Pigment Black 30, Pigment Black 32, Pigment Black33 or mixtures thereof.

In some embodiments, the pigment is lithopone, zinc sulfide, bariumsulfate, cobalt oxide, yellow iron oxide, orange iron oxide, red ironoxide, brown iron oxide, hematite, black iron oxide, micaceous ironoxide, chromium (III) green, ultramarine blue, ultramarine violet,ultramarine pink, cyanide iron blue, cadmium pigments or lead chromatepigments.

In some embodiments, the pigment is complex inorganic color pigments(CICP) such as spinel pigments, rutile pigments, zircon pigments orbismuth vanadate yellow. In some embodiments, useful spinel pigmentsinclude but are not limited to: Zn(Fe,Cr)2O4 brown, CoAl2O4 blue,Co(AlCr)2O4 blue-green, Co2TiO4 green, CuCr2O4 black or(Ni,Mn,Co)(Cr,Fe)2O4 black. In some embodiments, useful rutile pigmentsinclude but are not limited to: Ti—Ni—Sb yellow, Ti—Mn—Sb brown,Ti—Cr—Sb buff, zircon pigments or bismuth vanadate yellow.

In another embodiment, the pigment is an organic pigment. In someembodiments, useful organic pigments include but are not limited to:Aniline black (Pigment Black 1), Anthraquinone black, Monoazo type,Diazo type, Benzimidazolones, Diarylide yellow, Monoazo yellow salts,Dinitaniline orange, Pyrazolone orange, Azo red, Naphthol red, Azocondensation pigments, Lake pigments, Copper Phthalocyanine blue, CopperPhthalocyanine green, Quinacridones, Diaryl Pyrrolopyrroles,Aminoanthraquinone pigments, Dioxazines, Isoindolinones, Isoindolines,Quinophthalones, phthalocyanine pigments, idanthrone pigments, pigmentviolet 1, pigment violet 3, pigment violet 19 or pigment violet 23. Inyet another embodiment, the organic pigment is a Vat dye pigment, suchas but not limited to: perylene, perylene black, perinones orthioindigo. A uniform dispersion of isolated, individual pigmentparticles (aggregates) tends to produce uniform color intensity. In someembodiments the pigment is milled. In some embodiments, the meanparticle size of the pigment is between (and optionally including) anytwo of the following sizes: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and1.0 microns. In some embodiments, luminescent (fluorescent orphosphorescent), or pearlescent pigments can be used, alone, or incombination with other pigments or dyes.

In some embodiments, the first polyimide layer further comprises 1 to 20wt % of a matting agent selected from silica, alumina, zirconia, boronnitride, barium sulfate, polyimide particles, calcium phosphate, talc ormixtures thereof. In another embodiment, the first polyimide layerfurther comprises 1 to 20 wt % of a matting agent that is a carbon blackhaving a mean particle size from 2 to 9 micrometers. In yet anotherembodiment, the first polyimide layer further comprises 1 to 20 wt % ofa matting agent, the matting agent being a mixture of

-   -   i) carbon black having a mean particle size from 2 to 9 microns;        and    -   ii) silica, alumina, zirconia, boron nitride, barium sulfate,        polyimide particles, calcium phosphate, talc or mixtures        thereof.

In some embodiments, the first polyimide layer is Kapton® MBC polyimidefilm manufactured by DuPont.

In some embodiments, the first polyimide layer comprises:

-   -   i) a chemically converted polyimide in an amount from 71 to 96        wt %, the chemically converted polyimide being derived from:        -   a. at least 50 mole percent of an aromatic dianhydride,            based upon a total dianhydride content of the polyimide, and        -   b. at least 50 mole percent of an aromatic diamine, based            upon a total diamine content of the polyimide;    -   ii) a low conductivity carbon black present in an amount from 2        to 9 wt %; and    -   iii) a matting agent that:        -   a. is present in an amount from 1.6 to 10 wt %,        -   b. has a median particle size from 1.3 to 10 microns, and        -   c. has a density from 2 to 4.5 g/cc.

In a chemical conversion process, the polyamic acid solution is eitherimmersed in or mixed with conversion (imidization) chemicals. In oneembodiment, the conversion chemicals are tertiary amine catalysts(accelerators) and anhydride dehydrating materials. In one embodiment,the anhydride dehydrating material is acetic anhydride, which is oftenused in molar excess relative to the amount of amic acid (amide acid)groups in the polyamic acid, typically about 1.2 to 2.4 moles perequivalent of polyamic acid. In one embodiment, a comparable amount oftertiary amine catalyst is used.

Alternatives to acetic anhydride as the anhydride dehydrating materialinclude: i. other aliphatic anhydrides, such as, propionic, butyric,valeric, and mixtures thereof; ii. anhydrides of aromatic monocarboxylicacids; iii. Mixtures of aliphatic and aromatic anhydrides; iv.carbodimides; and v. aliphatic ketenes (ketenes may be regarded asanhydrides of carboxylic acids derived from drastic dehydration of theacids).

In one embodiment, the tertiary amine catalysts are pyridine andbeta-picoline and are typically used in amounts similar to the moles ofanhydride dehydrating material. Lower or higher amounts may be useddepending on the desired conversion rate and the catalyst used. Tertiaryamines having approximately the same activity as the pyridine, andbeta-picoline may also be used. These include alpha picoline;3,4-lutidine; 3,5-lutidine; 4-methyl pyridine; 4-isopropyl pyridine;N,N-dimethylbenzyl amine; isoquinoline; 4-benzyl pyridine,N,N-dimethyldodecyl amine, triethyl amine, and the like. A variety ofother catalysts for imidization are known in the art, such asimidazoles, and may be useful in accordance with the present disclosure.

The conversion chemicals can generally react at about room temperatureor above to convert polyamic acid to polyimide. In one embodiment, thechemical conversion reaction occurs at temperatures from 15° C. to 120°C. with the reaction being very rapid at the higher temperatures andrelatively slower at the lower temperatures.

In one embodiment, the chemically treated polyamic acid solution can becast or extruded onto a heated conversion surface or substrate. In oneembodiment, the chemically treated polyamic acid solution can be cast onto a belt or drum. The solvent can be evaporated from the solution, andthe polyamic acid can be partially chemically converted to polyimide.The resulting solution then takes the form of a polyamic acid-polyimidegel. Alternately, the polyamic acid solution can be extruded into a bathof conversion chemicals consisting of an anhydride component(dehydrating agent), a tertiary amine component (catalyst) or both withor without a diluting solvent. In either case, a gel film is formed andthe percent conversion of amic acid groups to imide groups in the gelfilm depends on contact time and temperature but is usually about 10 to75 percent complete. For curing to a solids level greater than 98%, thegel film typically must be dried at elevated temperature (from about200° C., up to about 550° C.), which will tend to drive the imidizationto completion. In some embodiments, the use of both a dehydrating agentand a catalyst is preferred for facilitating the formation of a gel filmand achieve desired conversion rates.

Second Polyimide Layer

The second polyimide layer comprises 25 to 50 wt % of a polyimidederived from at least 50 mole percent of an aromatic dianhydride, basedupon a total dianhydride content of the polyimide, and at least 50 molepercent of an aromatic diamine based upon a total diamine content of thepolyimide. In some embodiments, the second polyimide layer comprisesbetween and including any two of the following: 25, 30, 35, 40, 45 and50 wt % of a polyimide. In another embodiment, the second polyimidelayer comprises 33 to 39 wt % of a polyimide.

In one embodiment, the aromatic dianhydride is selected from the groupconsisting of:

-   pyromellitic dianhydride;-   3,3′,4,4′-biphenyl tetracarboxylic dianhydride;-   3,3′,4,4′-benzophenone tetracarboxylic dianhydride;-   4,4′-oxydiphthalic anhydride;-   3,3′,4,4′-diphenyl sulfone tetracarboxylic dianhydride;-   2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane;-   Bisphenol A dianhydride; and-   mixtures and derivatives thereof.    In another embodiment, the aromatic dianhydride is selected from the    group consisting of:-   2,3,6,7-naphthalene tetracarboxylic dianhydride;-   1,2,5,6-naphthalene tetracarboxylic dianhydride;-   2,2′,3,3′-biphenyl tetracarboxylic dianhydride;-   2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;-   bis(3,4-dicarboxyphenyl) sulfone dianhydride;-   3,4,9,10-perylene tetracarboxylic dianhydride;-   1,1-bis(2,3-dicarboxyphenyl) ethane dianhydride;-   1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride;-   bis(2,3-dicarboxyphenyl) methane dianhydride;-   bis(3,4-dicarboxyphenyl) methane dianhydride;-   oxydiphthalic dianhydride;-   bis(3,4-dicarboxyphenyl) sulfone dianhydride;-   mixtures and derivatives thereof.

In some embodiments, examples of suitable aliphatic dianhydrides includebut are not limited to: cyclobutane dianhydride;[1S*,5R*,6S*]-3-oxabicyclo[3.2.1]octane-2,4-dione-6-spiro-3-(tetrahydrofuran-2,5-dione);and mixtures thereof.

In some embodiments, the aromatic diamine is selected from the groupconsisting of: 3,4′-oxydianiline; 1,3-bis-(4-aminophenoxy) benzene;4,4′-oxydianiline; paraphenylenediamine; 1,3-diaminobenzene;2,2′-bis(trifluoromethyl) benzidene; 4,4′-diaminobiphenyl;4,4′-diaminodiphenyl sulfide; 9,9′-bis(4-amino)fluorine; mixtures andderivatives thereof.

In another embodiment, the aromatic diamine is selected from a groupconsisting of: 4,4′-diaminodiphenyl propane; 4,4′-diamino diphenylmethane; benzidine; 3,3′-dichlorobenzidine; 3,3′-diamino diphenylsulfone; 4,4′-diamino diphenyl sulfone; 1,5-diamino naphthalene;4,4′-diamino diphenyl diethylsilane; 4,4′-diamino diphenysilane;4,4′-diamino diphenyl ethyl phosphine oxide; 4,4′-diamino diphenylN-methyl amine; 4,4′-diamino diphenyl N-phenyl amine; 1,4-diaminobenzene(paraphenylene diamine); 1,2-diaminobenzene; mixtures and derivativesthereof.

In some embodiments, examples of suitable aliphatic diamines include:hexamethylene diamine, dodecane diamine, cyclohexane diamine andmixtures thereof.

In one embodiment, the second polyimide layer comprises a polyimidederived from pyromellitic dianhydride and 4,4′-oxydianiline or derivedfrom pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine. In another embodiment, the second polyimide layercomprises a polyimide derived from 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine. In another embodiment, the second polyimide layercomprises a polyimide derived from i) blocks of pyromellitic dianhydrideand 4,4′-oxydianiline and ii) blocks of pyromellitic dianhydride andparaphenylenediamine. In yet another embodiment, the second polyimidelayer comprises a polyimide derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 4,4′-oxydianilineand paraphenylenediamine. In yet another embodiment, the first polyimidelayer comprises a polyimide derived from pyromellitic dianhydride and4,4′-oxydianiline, and the second polyimide layer comprises a polyimidederived from

-   -   i) pyromellitic dianhydride and 4,4′-oxydianiline, or derived        from    -   ii) pyromellitic dianhydride, 4,4′-oxydianiline and        paraphenylenediamine, or derived from    -   iii) blocks of pyromellitic dianhydride and 4,4′-oxydianiline        and blocks of pyromellitic dianhydride and paraphenylenediamine,        or derived from    -   iv) 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromellitic        dianhydride, 4,4′-oxydianiline and paraphenylenediamine.

In some embodiments, the second polyimide layer is thinner than thefirst polyimide layer. Typically, the second polyimide layer is highlyfilled, and the first polyimide layer must provide mechanical support.Thus it is desirable to have a thin second polyimide layer. In someembodiments, the second polyimide layer is from 0.5 to 20 microns thick.In some embodiments, the second polyimide layer is between and includingany two of the following thicknesses: 0.5, 1, 5, 10, 15, and 20 micronsthick. In yet another embodiment, the second layer is from 0.7 to 10microns thick. In some embodiments, the second layer is from 0.7 to 3microns thick.

The second layer is in direct contact with the first polyimide layer.The term “direct contact” is intended to mean two surfaces adjacent toeach other without an intervening material or adhesive layer between thetwo surfaces.

The second polyimide layer comprises greater than 0 and less than 20 wt% of at least one submicron carbon black. The term “submicron” isintended to mean less than one micron in all dimensions. In anotherembodiment, the second polyimide layer comprises from 5 to 15 wt % of atleast one submicron carbon black. In another embodiment, the secondpolyimide layer comprises greater than 7 and less than 11 wt % of atleast one submicron carbon black. In another embodiment, the secondpolyimide layer comprises from 8 to 10 wt % of at least one submicroncarbon black. The submicron carbon black, for the purpose of the presentdisclosure, is intended to be the colorant. One of ordinary skill in theart could also envision the use of other colorants (pigments or dyes) tocreate any desired color. In some embodiments, the same pigment or dyeused in the second polyimide layer may be used in the first polyimidelayer. In yet another embodiment, the colorant in the second polyimidelayer could be different from any colorant that may be used in the firstpolyimide layer.

The second polyimide layer comprises 15 to 35 wt % of polyimide particlematting agent. In some embodiments, the second polyimide layer comprisesbetween and including any two of the following: 15, 16, 17, 18, 19, 20,25, 30, 31, 32, 33, 34 and 35 wt % of polyimide particle matting agent.In another embodiment, comprises 19 to 31 wt % of polyimide particlematting agent. In some embodiments, the second polyimide layer comprisesa mixture of polyimide particle matting agents or a mixture of polyimideparticle matting agent and another matting agent such as, silica,alumina, zirconia, boron nitride, barium sulfate, calcium phosphate andtalc.

The polyimide particle matting agent has a median particle size of 2 to11 microns. In some embodiments, the polyimide particle matting agenthas a median particle size between and including any two of thefollowing: 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 microns. In someembodiments the average particle size is 2 to 11 microns. The particlesize of the polyimide particle matting agent can be measured in theslurries by laser diffraction using either a Horiba LA-930 (Horiba,Instruments, Inc., Irvine Calif.) or a Malvern Mastersizer 3000 (MalvernInstruments, Inc., Westborough, Mass.).

The polyimide particle matting agent is derived from at least onearomatic dianhydride and at least one aromatic diamine. In oneembodiment, the polyimide particle matting agent is derived frompyromellitic dianhydride and 4,4′-oxydianiline.

In some embodiments, the polyimide particle matting agent is a pigmentedpolyimide particle matting agent. Pigmented polyimide particles arecomprised of a polyimide and a colorant. Pigmented polyimide particleshave a color different from the polyimide by itself. Virtually anycolorant can be used, including but not limited to inorganic pigments,complex inorganic color pigments, organic pigments, and dyes. Usefulblack colorants include carbon black, graphite, aniline black, andperylene black. Useful white colorants include titanium dioxide. Thecolorant may be incorporated into the polyimide particles, such as byabsorption, or dispersed as a separate phase within the polyimideparticles. Some or all of the colorant may be on the surface of thepolyimide particles. The surface of the particles may be partially orcompletely covered with the colorant. Pigmented polyimide particles maybe produced by a variety of methods, including but not limited to thefollowing: incorporation of the colorant into the polyimide particlesduring the process of particle formation by precipitation from solution;absorption, imbibition, or diffusion of the colorant into the polyimideparticles; coating of the colorant onto the polyimide particles. Thepigmented polyimide particles may contain from 1 wt % to 70 wt %colorant. In some embodiments, the pigmented polyimide particles maycontain from 1 wt % to 50 wt % colorant. Pigmented polyimide particlematting agents useful in the present disclosure include those disclosedin U.S. Pat. application 2014/0220335, the disclosure of which arehereby incorporated by reference.

In some embodiments, the second polyimide layer comprises 15 to 35 wt %of pigmented polyimide particle matting agent. In some embodiments, thesecond polyimide layer comprises between and including any two of thefollowing: 15, 16, 17, 18, 19, 20, 25, 30, 31, 32, 33, 34 and 35 wt % ofpigmented polyimide particle matting agent. In another embodiment,comprises 19 to 31 wt % of pigmented polyimide particle matting agent.

In some embodiments, the pigmented polyimide particle matting agent isderived from pyromellitic dianhydride and 4,4′-oxydianiline. In someembodiments, the pigmented polyimide particle matting agent is derivedfrom pyromellitic dianhydride and 4,4′-oxydianiline and graphite as thecolorant (pigment).

In some embodiments, the polyimide particle matting agent is derivedfrom pyromellitic dianhydride and 4,4′-oxydianiline and the polyimide ofthe second polyimide layer is derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine. In some embodiments, thepigmented polyimide particle matting agent is derived from pyromelliticdianhydride, 4,4′-oxydianiline and colorant and the polyimide of thesecond polyimide layer is derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine. In some embodiments, thepigmented polyimide particle matting agent is derived from pyromelliticdianhydride, 4,4′-oxydianiline and graphite and the polyimide of thesecond polyimide layer is derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine. MULTILAYER FILM

The multilayer film in accordance with the present disclosure has afirst polyimide layer and a second polyimide layer as described above.The multilayer film has an L* color less than 30 and a 60 degree glossvalue less than 10 as well as durability to handling and circuitprocessing. The L* color is measured using a HunterLab ColorQuest® XEcolor meter (Hunter Associates Laboratory, Inc.) in the reflectance,specular included mode and reported in the CIELAB 10°/D65 system, as L*,a*, b*. A L* value of 0 is pure black, while a L* value of 100 is purewhite. The 60 degree gloss was measured using a Micro-TRI-glossglossmeter (from BYK-Gardner).

FIG. 1 illustrates one embodiment of the present disclosure, amultilayer film comprising an adhesive layer 60 in direct contact withthe first polyimide layer 10 opposite the second polyimide layer 20,wherein the second polyimide layer comprises a polyimide particlematting agent 30, a submicron carbon black 40 and a submicron fumedmetal oxide 50. In some embodiments, the adhesive layer is an epoxyadhesive selected from the group consisting of: Bisphenol A type epoxyresin, cresol novolac type epoxy resin, phosphorus containing epoxyresin, and mixtures thereof. Typically, an adhesive layer is as thick asor thicker than the first polyimide layer or the second polyimide layer.In some embodiments the adhesive layer is from 8 to 300 microns thick.

In some embodiments, the adhesive is a mixture of two or more epoxyresins. In some embodiments, the adhesive is a mixture of the same epoxyresin having different molecular weights.

In some embodiments, the epoxy adhesive contains a hardener. In someembodiments, the epoxy adhesive contains a catalyst. In someembodiments, the epoxy adhesive contains an elastomer toughening agent.In some embodiments, the epoxy adhesive contains a flame retardant.

In some embodiments, the multilayer film further comprises a thirdpolyimide layer. In some embodiments, the third polyimide layer is from0.5 to 20 microns thick. In another embodiment, the third polyimidelayer is between and including any two of the following thicknesses:0.5, 1, 5, 10, 15 and 20 micron thick. In some embodiments, the thirdpolyimide layer is from 0.7 to 10 microns thick. In some embodiments,the third polyimide layer is from 0.7 to 3 microns thick. In someembodiments, the multilayer film further comprises a third polyimidelayer from 0.5 to 20 microns thick in direct contact with the firstpolyimide layer opposite the second polyimide layer.

A third polyimide layer, is particularly desired when the multilayerfilm is coextruded. The third polyimide layer, when similar to or thesame as the second polyimide layer helps prevent curl. The thirdpolyimide layer may be the same as, or different from, the secondpolyimide layer.

In some embodiments, the multilayer film further comprises a thirdpolyimide layer from 0.5 to 20 microns thick in direct contact with thefirst polyimide layer opposite the second polyimide layer, the thirdpolyimide layer comprising:

-   -   i) a polyimide derived from at least 50 mole percent of an        aromatic dianhydride, based upon a total dianhydride content of        the polyimide, and at least 50 mole percent of an aromatic        diamine based upon a total diamine content of the polyimide; and    -   ii) a matting agent or mixture thereof.

In one embodiment, the matting agent in the third polyimide layer isselected from silica, alumina, zirconia, boron nitride, barium sulfate,polyimide particles, calcium phosphate, talc or mixtures thereof. Inanother embodiment, the matting agent in the third polyimide layer is acarbon black having a mean particle size from 2 to 9 microns. In yetanother embodiment, the matting agent in the third polyimide layer is amixture of

-   -   i) carbon black having a mean particle size from 2 to 9 microns;        and    -   ii) silica, alumina, zirconia, boron nitride, barium sulfate,        polyimide particles, calcium phosphate, talc or mixtures        thereof. In another embodiment, the matting agent in the third        polyimide layer is polyimide particle matting agent. In yet        another embodiment, the matting agent in the third polyimide        layer is pigmented polyimide particle matting agent.

In another embodiment, the third polyimide layer comprises 15 to 35 wt %of polyimide particle matting agent. In some embodiments, the thirdpolyimide layer comprises between and including any two of thefollowing: 15, 16, 17, 18, 19, 20, 25, 30, 31, 32, 33, 34 and 35 wt % ofpolyimide particle matting agent. In another embodiment, the thirdpolyimide layer comprises 19 to 31 wt % of polyimide particle mattingagent. In some embodiments, the third polyimide layer comprises amixture of polyimide particle matting agents or a mixture of polyimideparticle matting agent and another matting agent such as, silica,alumina, zirconia, boron nitride, barium sulfate, calcium phosphate andtalc.

The polyimide particle matting agent has a median particle size of 2 to11 microns. In some embodiments, the polyimide particle matting agenthas a median particle size between and including any two of thefollowing: 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 microns. In someembodiments the average particle size is 2 to 11 microns. The particlesize of the polyimide particle matting agent can be measured in theslurries by laser diffraction using either a Horiba LA-930 (Horiba,Instruments, Inc., Irvine Calif.) or a Malvern Mastersizer 3000 (MalvernInstruments, Inc., Westborough, Mass.).

The polyimide particle matting agent is derived from at least onearomatic dianhydride and at least one aromatic diamine. In oneembodiment, the polyimide particle matting agent is derived frompyromellitic dianhydride and 4,4′-oxydianiline.

In some embodiments, the polyimide particle matting agent is a pigmentedpolyimide particle matting agent. Pigmented polyimide particles arecomprised of a polyimide and a colorant. Pigmented polyimide particleshave a color different from the polyimide by itself. Virtually anycolorant can be used, including but not limited to inorganic pigments,complex inorganic color pigments, organic pigments, and dyes. Usefulblack colorants include carbon black, graphite, aniline black, andperylene black. Useful white colorants include titanium dioxide. Thecolorant may be incorporated into the polyimide particles, such as byabsorption, or dispersed as a separate phase within the polyimideparticles. Some or all of the colorant may be on the surface of thepolyimide particles. The surface of the particles may be partially orcompletely covered with the colorant. Pigmented polyimide particles maybe produced by a variety of methods, including but not limited to thefollowing: incorporation of the colorant into the polyimide particlesduring the process of particle formation by precipitation from solution;absorption, imbibition, or diffusion of the colorant into the polyimideparticles; coating of the colorant onto the polyimide particles. Thepigmented polyimide particles may contain from 1 to 70 wt % colorant. Insome embodiments, the pigmented polyimide particles may contain from 1to 50 wt % colorant. Pigmented polyimide particle matting agents usefulin the present disclosure include those disclosed in U.S. Pat.application 2014/0220335, the disclosure of which are herebyincorporated by reference.

In some embodiments, the third polyimide layer comprises 15 to 35 wt %of pigmented polyimide particle matting agent. In some embodiments, thethird polyimide layer comprises between and including any two of thefollowing: 15, 16, 17, 18, 19, 20, 25, 30, 31, 32, 33, 34 and 35 wt % ofpigmented polyimide particle matting agent. In another embodiment,comprises 19 to 31 wt % of pigmented polyimide particle matting agent.

In some embodiments, the pigmented polyimide particle matting agent isderived from pyromellitic dianhydride and 4,4′-oxydianiline. In someembodiments, the pigmented polyimide particle matting agent is derivedfrom pyromellitic dianhydride and 4,4′-oxydianiline and graphite as thecolorant (pigment).

In some embodiments, the polyimide particle matting agent is derivedfrom pyromellitic dianhydride and 4,4′-oxydianiline and the polyimide ofthe third polyimide layer is derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine. In some embodiments, thepigmented polyimide particle matting agent is derived from pyromelliticdianhydride, 4,4′-oxydianiline and colorant and the polyimide of thethird polyimide layer is derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine. In some embodiments, thepigmented polyimide particle matting agent is derived from pyromelliticdianhydride, 4,4′-oxydianiline and graphite and the polyimide of thethird polyimide layer is derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine.

In one embodiment, the third polyimide layer comprises a polyimidederived from pyromellitic dianhydride and 4,4′-oxydianiline. In anotherembodiment, the third polyimide layer comprises a polyimide derived frompyromellitic dianhydride, 4,4′-oxydianiline and paraphenylenediamine. Inanother embodiment, the second polyimide layer comprises a polyimidederived from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride,pyromellitic dianhydride, 4,4′-oxydianiline and paraphenylenediamine. Inanother embodiment, the third polyimide layer comprises a polyimidederived from i) blocks of pyromellitic dianhydride and 4,4′-oxydianilineand ii) blocks of pyromellitic dianhydride and paraphenylenediamine.

In another embodiment, the multilayer film further comprises a thirdpolyimide layer from 0.5 to 20 microns thick in direct contact with thefirst polyimide layer opposite the second polyimide layer; the thirdpolyimide layer comprises:

-   -   i) 25 to 50 wt % of a polyimide derived from at least 50 mole        percent of an aromatic dianhydride, based upon a total        dianhydride content of the polyimide, and at least 50 mole        percent of an aromatic diamine based upon a total diamine        content of the polyimide;    -   ii) 15 to 35 wt % of polyimide particle matting agent;    -   iii) greater than 0 and less than 20 wt % of at least one        submicron carbon black; and    -   iv) 15 to 50 wt % of at least one submicron fumed metal oxide.

FIG. 2 illustrates another embodiment of the present disclosure, amultilayer film comprising a third polyimide layer 70 in direct contactwith the first polyimide layer 10, an adhesive layer 60 in directcontact with the second polyimide layer 20 on a surface of the secondpolyimide layer furthest from the first polyimide layer 10, wherein thesecond polyimide layer and the third polyimide layer comprises apolyimide particle matting agent 30, a submicron carbon black 40 and asubmicron fumed metal oxide 50. In yet another embodiment, an adhesivelayer 60 may be in direct contact with the third polyimide layer 70 on asurface of the third polyimide furthest from the first polyimide layer10.

One embodiment of the present disclosure is a method of producing amultilayer film having an L* color less than 30 and a 60 degree glossvalue less than 10; the method comprising:

-   -   a. providing a first polyimide layer from 8 to 130 microns        thick;    -   b. coating a second polyimide layer from 0.5 to 8 microns thick        on to the first polyimide layer; the second polyimide layer        comprising:        -   i) 25 to 50 wt % of a polyimide derived from at least 50            mole percent of an aromatic dianhydride, based upon a total            dianhydride content of the polyimide, and at least 50 mole            percent of an aromatic diamine based upon a total diamine            content of the polyimide        -   ii) 15 to 35 wt % of polyimide particle matting agent;        -   iii) greater than 0 and less than 20 wt % of at least one            submicron carbon black; and        -   iv) 15 to 50 wt % of at least one submicron fumed metal            oxide.

The first polyimide layer and the second polyimide layer of the presentdisclosure can be made by any well-known method in the art for makingfilled polyimide films. In some embodiments, the first polyimide layerand the second polyimide layer are made by a thermal conversion process(thermally imidized) in which the polyamic acid solution is heated totemperatures typically greater than 250° C. to convert the polyamic acidto a polyimide. In another embodiment, the first polyimide layer and thesecond polyimide layer are made by a chemical conversion process(chemically imidized). In one embodiment, one such method includespreparing a pigment slurry. The slurry may or may not be milled using aball mill or continuous media mill to reach the desired particle size.The slurry may or may not be filtered to remove any residual largeparticles. A polyamic acid prepolymer solution is prepared by reactingdianhydride with a slight excess of diamine. The polyamic acid solutionis mixed in a high shear mixer with the pigment slurry. The amount ofthe polyamic acid solution, pigment slurry, and finishing solution canbe adjusted to achieve the desired loading levels of pigment and thedesired viscosity for film formation. “Finishing solution” hereindenotes a dianyhdride in a polar aprotic solvent which is added to aprepolymer solution to increase the molecular weight and viscosity. Thedianhydride used is typically the same dianhydride used (or one of thesame dianhydrides when more than one is used) to make the prepolymer.The mixture can be metered through a slot die and cast or manually castonto a smooth stainless steel belt or substrate to produce a gel film.Conversion chemicals can be metered in before casting using a slot die.For conversion to greater than 98 percent solids level, the gel filmtypically must be dried at elevated temperature (convective heating from200-300° C. and radiant heating from 400-800° C.), which will tend todrive the imidization to completion. In yet another embodiment, thefirst polyimide layer and the second polyimide layer are independentlymade by either a thermal conversion process or a chemical conversionprocess.

The multilayer film of the present disclosure can be prepared by anywell-known method such as but not limited to coextrusion, lamination(laminating single layers together), coating and combinations thereof. Adescription of a coextrusion process for preparing multilayer polyimidefilms is provided in EP 0659553 A1 to Sutton et al. Coating methodsinclude, but are not limited to, spray coating, curtain coating, knifeover roll, air knife, extrusion/slot die, gravure, reverse gravure,offset gravure, roll coating, and dip/immersion.

In some embodiments, the multilayer film is prepared by simultaneouslyextruding (coextruding) the first polyimide layer and the secondpolyimide layer. In some embodiments, the multilayer film is prepared bysimultaneously extruding (coextruding) the first polyimide layer, thesecond polyimide layer and the third polyimide layer. In someembodiments, the layers are extruded through a single or multi-cavityextrusion die. In another embodiment, the multilayer film is producedusing a single-cavity die. If a single-cavity die is used, the laminarflow of the streams should be of high enough viscosity to preventcomingling of the streams and to provide even layering. In someembodiments, the multilayer film is prepared by casting from the slotdie onto a moving stainless steel belt. In one embodiment, the belt isthen passed through a convective oven, to evaporate solvent andpartially imidize the polymer, to produce a “green” film. The green filmcan be stripped off the casting belt and wound up. The green film canthen be passed through a tenter oven to produce a fully cured polyimidefilm. In some embodiments, during tentering, shrinkage can be minimizedby constraining the film along the edges (i.e. using clips or pins).

In some embodiments, the multilayer film is made by coating a solutionof matting agent, submicron carbon black and submicron fumed metal oxideslurries and polyamic acid on the first polyimide layer. The coating isheated to dry. The resulting multilayer film is placed on a pin frame tohold it flat. The coating can be cured in a batch or continuous ovencapable of heating to at least 250° C. The oven temperature is ramped to320° C. over a period of 45 to 60 minutes, then transferred to a 400° C.oven and held for 5 minutes. In some embodiments, chemical imidizationcatalysts and/or dehydrating agents can be added to the coatingsolution.

In yet another embodiment of the present disclosure is, a method ofreducing the amount of colorant in a multilayer film and achieving an L*color less than 30 and a 60 degree gloss value less than 10, the methodcomprising;

-   -   a) providing a first polyimide layer or a first polyamic acid        solution or a first polyamic acid green film derived from        pyromellitic dianhydride and 4,4′-oxydianiline;    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black; wherein the polyamic acid is derived from pyromellitic        dianhydride and 4,4′-oxydianiline, or derived from pyromellitic        dianhydride, 4,4′-oxydianiline and paraphenylenediamine, or        derived from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride,        pyromellitic dianhydride, 4,4′-oxydianiline and        paraphenylenediamine, or derived from i) blocks of pyromellitic        dianhydride and 4,4′-oxydianiline and ii) blocks of pyromellitic        dianhydride and paraphenylenediamine;    -   c) adding 15 to 50 wt % of at least one submicron fumed metal        oxide to the second polyamic acid solution;    -   d) coating the polyamic acid solution formed in step c on to the        first polyimide layer or, coating the polyamic acid solution        formed in step c on to the first polyamic acid green film; or        coextruding the polyamic acid solution formed in step c and the        first polyamic acid solution; and    -   f) imidizing the coating formed in step d to form a second        polyimide layer on the first polyimide layer, or imidizing the        coating formed in step d and the first polyamic acid green film        to form a first polyimide layer and a second polyimide layer, or        imidizing the coextruded layers formed in step d to form a first        polyimide layer and a second polyimide layer; and wherein the        second polyimide layer is in direct contact with the first        polyimide layer.

Another embodiment of the present disclosure is a method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:

-   -   a) providing a component selected from the group consisting of:        a first polyimide layer, a first polyamic acid solution and a        first polyamic acid green film;    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black;    -   c) adding at least one submicron fumed metal oxide to the second        polyamic acid solution;    -   d) forming a multilayer composite by coating the polyamic acid        solution formed in step c on to the first polyimide layer, or        coating the polyamic acid solution formed in step c on to the        first polyamic acid green film, or coextruding the polyamic acid        solution formed in step c and the first polyamic acid solution;        and    -   f) imidizing the composite formed in step d to produce a first        polyimide layer and a second polyimide layer.

The submicron fumed metal oxide or mixtures thereof can be addeddirectly to the second polyamic acid solution or by preparing asubmicron fumed metal oxide slurry which is then added to the secondpolyamic acid solution. In some embodiments, the second polyamic acidsolution is added to the submicron fumed metal oxide slurry. In someembodiments, the polyimide particle matting agent, the submicron carbonblack and the submicron fumed metal oxide (and slurries thereof) may becombined in any order before coating the polyamic acid solution formedin step c on to the first polyimide layer; or coextruding the polyamicacid solution formed in step c and the first polyamic acid solution.

The polyamic acid formed in step c can be coated by methods well knownin the art such as, but not limited to, spray coating, curtain coating,knife over roll, air knife, extrusion/slot die, gravure, reversegravure, offset gravure, roll coating, and dip/immersion.

The coating or coextruded layers can be imidized by thermal conversionor chemical conversion as previously described.

In some embodiments, the first polyamic acid solution is partially driedand partly imidized to form a first polyamic acid green film. Then thepolyamic acid solution formed in step c is coated on the first polyamicacid green film and both layers are imidized.

Another embodiment of the present disclosure is a method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:

-   -   a) providing a component selected from the group consisting of:        a first polyimide layer, a first polyamic acid solution and a        first polyamic acid green film;    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black;    -   c) adding at least one submicron fumed metal oxide to the second        polyamic acid solution;    -   d) forming a multilayer composite by coating the polyamic acid        solution formed in step c on to the first polyimide layer, or        coating the polyamic acid solution formed in step c on to the        first polyamic acid green film, or coextruding the polyamic acid        solution formed in step c and the first polyamic acid solution;        and    -   f) imidizing the composite formed in step d to produce a first        polyimide layer and a second polyimide layer; and wherein the        second polyimide layer is in direct contact with the first        polyimide layer.

Another embodiment of the present disclosure is a method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:

-   -   a) providing a component selected from the group consisting of:        a first polyimide layer, a first polyamic acid solution and a        first polyamic acid green film and derived from pyromellitic        dianhydride and 4,4′-oxydianiline,    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black;    -   c) adding at least one submicron fumed metal oxide to the second        polyamic acid solution;    -   d) forming a multilayer composite by coating the polyamic acid        solution formed in step c on to the first polyimide layer, or        coating the polyamic acid solution formed in step c on to the        first polyamic acid green film, or coextruding the polyamic acid        solution formed in step c and the first polyamic acid solution;        and    -   f) imidizing the composite formed in step d to produce a first        polyimide layer and a second polyimide layer.

In yet another embodiment, the method of reducing amount of colorant ina multilayer film wherein the second polyimide layer comprises apolyimide derived from pyromellitic dianhydride and 4,4′-oxydianiline orderived from pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine or derived from 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine or derived from i) blocks of pyromelliticdianhydride and 4,4′-oxydianiline and ii) blocks of pyromelliticdianhydride and paraphenylenediamine.

Another embodiment of the present disclosure is a method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:

-   -   a) providing a component selected from the group consisting of:        a first polyimide layer, a first polyamic acid solution and a        first polyamic acid green film and derived from pyromellitic        dianhydride and 4,4′-oxydianiline,    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black; wherein the polyamic acid is derived from pyromellitic        dianhydride and 4,4′-oxydianiline, or derived from pyromellitic        dianhydride, 4,4′-oxydianiline and paraphenylenediamine, or        derived from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride,        pyromellitic dianhydride, 4,4′-oxydianiline and        paraphenylenediamine, or derived from i) blocks of pyromellitic        dianhydride and 4,4′-oxydianiline and ii) blocks of pyromellitic        dianhydride and paraphenylenediamine;    -   c) adding at least one submicron fumed metal oxide to the second        polyamic acid solution;    -   d) forming a multilayer composite by coating the polyamic acid        solution formed in step c on to the first polyimide layer, or        coating the polyamic acid solution formed in step c on to the        first polyamic acid green film, or coextruding the polyamic acid        solution formed in step c and the first polyamic acid solution;        and    -   f) imidizing the composite formed in step d to produce a first        polyimide layer and a second polyimide layer.

Another embodiment of the present disclosure is a method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:

-   -   a) providing a component selected from the group consisting of:        a first polyimide layer, a first polyamic acid solution and a        first polyamic acid green film;    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black;    -   c) adding 15 to 50 wt % of at least one submicron fumed metal        oxide to the second polyamic acid solution;    -   d) forming a multilayer composite by coating the polyamic acid        solution formed in step c on to the first polyimide layer, or        coating the polyamic acid solution formed in step c on to the        first polyamic acid green film, or coextruding the polyamic acid        solution formed in step c and the first polyamic acid solution;        and    -   f) imidizing the composite formed in step d to produce a first        polyimide layer and a second polyimide layer.

Another embodiment of the present disclosure is a method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:

-   -   a) providing a component selected from the group consisting of:        a first polyimide layer, a first polyamic acid solution and a        first polyamic acid green film and derived from pyromellitic        dianhydride and 4,4′-oxydianiline,    -   b) providing a second polyamic acid solution containing polyamic        acid, polyimide particle matting agent, and submicron carbon        black; wherein the polyamic acid is derived from pyromellitic        dianhydride and 4,4′-oxydianiline, or derived from pyromellitic        dianhydride, 4,4′-oxydianiline and paraphenylenediamine, or        derived from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride,        pyromellitic dianhydride, 4,4′-oxydianiline and        paraphenylenediamine, or derived from i) blocks of pyromellitic        dianhydride and 4,4′-oxydianiline and ii) blocks of pyromellitic        dianhydride and paraphenylenediamine;    -   c) adding 15 to 50 wt % of at least one submicron fumed metal        oxide to the second polyamic acid solution;    -   d) forming a multilayer composite by coating the polyamic acid        solution formed in step c on to the first polyimide layer, or        coating the polyamic acid solution formed in step c on to the        first polyamic acid green film, or coextruding the polyamic acid        solution formed in step c and the first polyamic acid solution;        and    -   f) imidizing the composite formed in step d to produce a first        polyimide layer and a second polyimide layer.

When an amount, concentration, or other value or parameter is given aseither a range, preferred range or a list of upper preferable values andlower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. Numerical values are to be understood to have the precisionof the number of significant figures provided. For example, the number 1shall be understood to encompass a range from 0.5 to 1.4, whereas thenumber 1.0 shall be understood to encompass a range from 0.95 to 1.04,including the end points of the stated ranges. It is not intended thatthe scope of the invention be limited to the specific values recitedwhen defining a range.

In describing certain polymers it should be understood that sometimesapplicants are referring to the polymers by the monomers used to makethem or the amounts of the monomers used to make them. While such adescription may not include the specific nomenclature used to describethe final polymer or may not contain product-by-process terminology, anysuch reference to monomers and amounts should be interpreted to meanthat the polymer is made from those monomers, unless the contextindicates or implies otherwise.

The materials, methods, and examples herein are illustrative only and,except as specifically stated, are not intended to be limiting. Althoughmethods and materials similar or equivalent to those described hereincan be used, suitable methods and materials are described herein.

All publications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Unlessotherwise defined, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which this invention belongs. In case of conflict, the presentspecification, including definitions, will control.

Examples

Illustrative preparations and evaluations of films are described below.

Carbon Black Slurry (SB6 Carbon):

A carbon black slurry was prepared, consisting of 82 wt. % DMAC, 12 wt.% carbon black powder (Special Black 6, from Orion Engineered CarbonsLLC), and 6 wt. % dispersing agent (Byk 9077, from Byk Chemie). Theingredients were thoroughly mixed in a high speed disc-type disperser.The slurry was then processed in a bead mill to disperse anyagglomerates and to achieve the desired particle size. Median particlesize was 0.14 microns.

Fumed Alumina Slurry

A fumed alumina slurry was prepared, consisting of 76.3 wt. % DMAC, 19.8wt. % fumed alumina powder (Alu C805, from Evonik), and 3.9 wt. %dispersing agent (Disperbyk 180, from Byk Chemie). The ingredients werethoroughly mixed in a high speed disc-type disperser. The slurry wasthen processed in a bead mill to disperse any agglomerates and toachieve the desired particle size. Median particle size was 0.3 microns.

Polyimide Particle Slurry:

A polyimide particle slurry was prepared from a solution of PMDA/4,4′ODApolyamic acid in pyridine and heating the solution to precipitate thepolymer. The pyridine solvent was displaced with deionized water andthen comminuted in a high shear environment. The deionized water wasdisplaced with DMAc to a 3.6 wt. % solids concentration. Median particlesize was 4.0 microns.

Pigmented Polyimide Particle Slurry:

A pigmented polyimide particle slurry was prepared. Graphite powder wasdispersed in a solution of PMDA/4,4′ODA polyamic acid in pyridine. Themixture was heated to form a precipitate of polyimide particlescontaining 40 weight % graphite. The pyridine solvent was displaced withdeionized water, comminuted in a high shear environment, and then dried.The resulting powder was passed through a 325 mesh screen. The medianparticle size of the powder passing through the screen was 9.9 microns.The powder was dispersed in DMAC to form a 10 wt % dispersion ofpigmented polyimide particles.

Kapton® MBC is an opaque matte black polyimide film manufactured byDuPont. It is based on PMDA/4,4′ODA polyimide, and containsapproximately 5 wt. % carbon black and approximately 2 wt. % of a silicamatting agent. It is available in various thicknesses.

PMDA/4,4′ODA/PPD (100/70/30 Mole Ratio) Co-Polyamic Acid Solution:

PPD was dissolved in DMAC at 40-45° C. to a concentration ofapproximately 2.27 wt. %. After reducing the temperature to 30-40° C.,solid PMDA was added, with agitation, to achieve a PMDA:PPDstoichiometric ratio of approximately 0.99:1. The mixture was allowed toreact for 90 minutes, with agitation. The mixture was diluted toapproximately 5.8-6.5% solids by addition of DMAC. 4,4′ODA was thenadded, to achieve a 4,4′ODA:PPD mole ratio of 70:30, and allowed toreact for approximately 30 minutes at 40-45° C. Solid PMDA wasincrementally added, with agitation, and allowed to react forapproximately 2 hours at 40-45° C., to achieve a polymer viscosity of75-250 Poise. Polyamic acid solids was 19.5%-20.5%. The polymer solutionwas stored in a refrigerator until use.

Preparation of Multilayer Film Examples 1 Through 4

The First polyimide layer comprised Kapton® MBC film, as indicated inTable 1.

The Second polyimide layer was prepared using the filler slurries asdescribed above and indicated in Table 1. The slurries were thoroughlymixed with polyamic acid solution, described above and indicated inTable 1, in the appropriate ratio to produce the desired compositionafter curing. The resulting mixture was coated onto the First polyimidelayer using a stainless steel casting rod. The coating was dried on ahot plate at 100° C. until dry by visual inspection. The resultingmultilayer film was then placed on a pin frame to hold it flat, andplaced in a 120 □C oven. The oven temperature was ramped to 320 □C overa period of 45 to 60 minutes, then transferred to a 400 □C oven and heldfor 5 minutes, then removed from the oven and allowed to cool.

Compositions of the cured films were calculated from the composition ofthe components in the mixtures, excluding DMAC solvent (which is removedduring curing) and accounting for removal of water during conversion ofpolyamic acid to polyimide.

The 60 degree gloss was measured using a Micro-TRI-gloss glossmeter(from BYK-Gardner).

The L* color was measured using a HunterLab ColorQuest® XE color meter(Hunter Associates Laboratory, Inc.) in the reflectance, specularincluded mode. The instrument was standardized prior to each use. Colordata from the instrument were reported in the CIELAB 10°/D65 system, asL*, a*, b*. A L* value of 0 is pure black, while a L* value of 100 ispure white. Typically, a L* value difference of 1 unit is discernible tothe eye.

Particle size of filler particles in the slurries was measured by laserdiffraction using either a Horiba LA-930 (Horiba, Instruments, Inc.,Irvine Calif.) or a Malvern Mastersizer 3000 (Malvern Instruments, Inc.,Westborough, Mass.) particle size analyzer. DMAC was used as the carrierfluid.

Alcohol wipe test: The film was wiped 3 times with a towel which waswetted with isopropyl alcohol. A “Fail” grade was given if any colorantwas observed to transfer from the film to the towel. This test is ameasure of the suitability of the film with respect to durability toprocessing conditions for electronic circuit manufacture.

Results are shown in Table 1.

TABLE 1 2nd PI layer other Thickness First filler other (microns) PIcarbon matting other trade filler D50 First PI Second Layer black agentfiller name (microns) PI layer PI layer 1 MBC SB6 PI fumed Alu C805 0.3PMDA/ODA/PPD 25 0.7 particles alumina 2 MBC SB6 PI fumed Alu C805 0.3PMDA/ODA/PPD 25 2 particles alumina 3 MBC SB6 PI fumed Alu C805 0.3PMDA/ODA/PPD 25 1 particles alumina 4 MBC SB6 black PI fumed Alu C8050.3 PMDA/ODA/PPD 25 3 particles alumina Other filler wt % wt % wt %primary carbon matting other alcohol particle size black agent wt % PIfiller wipe test L* 60° gloss (nm) 1 8 31 33 20 pass 22.1 3.4 13 2 8 2539 20 pass 25.5 4.0 13 3 10 19 36 25 pass 23.61 5.6 13 4 10 19 36 25pass 28.68 4.7 13

The materials, methods, and examples herein are illustrative only and,except as specifically stated, are not intended to be limiting. Althoughmethods and materials similar or equivalent to those described hereincan be used in the practice or testing of the present invention,suitable methods and materials are described herein.

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that further activities may beperformed in addition to those described. Still further, the order inwhich each of the activities are listed are not necessarily the order inwhich they are performed. After reading this specification, skilledartisans will be capable of determining what activities can be used fortheir specific needs or desires.

In the foregoing specification, the invention has been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. All features disclosed in this specification may bereplaced by alternative features serving the same, equivalent or similarpurpose.

Accordingly, the specification is to be regarded in an illustrativerather than a restrictive sense and all such modifications are intendedto be included within the scope of the invention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims.

What is claimed is:
 1. A method of reducing the amount of colorant in amultilayer film and achieving an L* color less than 30 and a 60 degreegloss value less than 10, the method comprising: a) providing a firstpolyimide layer; b) providing a polyamic acid solution containingpolyamic acid, polyimide particle matting agent, and submicron carbonblack for forming a second polyimide layer; c) adding at least onesubmicron fumed metal oxide to the polyamic acid solution; d) coatingthe polyamic acid solution on to the first polyimide layer; and e)imidizing the coating to form the second polyimide layer on the firstpolyimide layer.
 2. The method of claim 1, wherein the first polyimidelayer is derived from pyromellitic dianhydride and 4,4′-oxydianiline, orderived from pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine.
 3. The method of claim 1, wherein the polyamicacid is derived from pyromellitic dianhydride and 4,4′-oxydianiline, orderived from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride andparaphenylenediamine, or derived from pyromellitic dianhydride,4,4′-oxydianiline and paraphenylenediamine, or derived from3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromelliticdianhydride, 4,4′-oxydianiline, or derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 4,4′-oxydianilineand paraphenylenediamine, or derived from i) blocks of pyromelliticdianhydride and 4,4′-oxydianiline and ii) blocks of pyromelliticdianhydride and paraphenylenediamine, or derived from pyromelliticdianhydride, oxydiphthalic dianhydride and 1,3-bis-(4-aminophenoxy)benzene, or a mixture thereof.
 4. The method of claim 1, wherein thesubmicron fumed metal oxide comprises fumed alumina, fumed silica or amixture thereof.
 5. A method of reducing the amount of colorant in amultilayer film and achieving an L* color less than 30 and a 60 degreegloss value less than 10, the method comprising: a) providing a polyamicacid green film for forming a first polyimide layer; b) providing apolyamic acid solution containing polyamic acid, polyimide particlematting agent, and submicron carbon black for forming a second polyimidelayer; c) adding at least one submicron fumed metal oxide to thepolyamic acid solution; d) coating the polyamic acid solution on to thepolyamic acid green film; and e) imidizing the coating and the polyamicacid green film to form the first and second polyimide layers.
 6. Themethod of claim 5, wherein the polyamic acid green film is derived frompyromellitic dianhydride and 4,4′-oxydianiline, or derived frompyromellitic dianhydride, 4,4′-oxydianiline and paraphenylenediamine. 7.The method of claim 5, wherein the polyamic acid is derived frompyromellitic dianhydride and 4,4′-oxydianiline, or derived from3,3′,4,4′-biphenyl tetracarboxylic dianhydride and paraphenylenediamine,or derived from pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine, or derived from 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, pyromellitic dianhydride, 4,4′-oxydianiline, or derivedfrom 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromelliticdianhydride, 4,4′-oxydianiline and paraphenylenediamine, or derived fromi) blocks of pyromellitic dianhydride and 4,4′-oxydianiline and ii)blocks of pyromellitic dianhydride and paraphenylenediamine, or derivedfrom pyromellitic dianhydride, oxydiphthalic dianhydride and1,3-bis-(4-aminophenoxy) benzene, or a mixture thereof.
 8. The method ofclaim 5, wherein the submicron fumed metal oxide comprises fumedalumina, fumed silica or a mixture thereof.
 9. A method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:a) providing a first polyamic acid solution containing a first polyamicacid for forming a first polyimide layer; b) providing a second polyamicacid solution containing a second polyamic acid, polyimide particlematting agent, and submicron carbon black for forming a second polyimidelayer; c) adding at least one submicron fumed metal oxide to the secondpolyamic acid solution; d) coextruding the second polyamic acid solutionand the first polyamic acid solution; and e) imidizing the coextrudedlayers to form the first and second polyimide layers.
 10. The method ofclaim 9, wherein the first polyamic acid is derived from pyromelliticdianhydride and 4,4′-oxydianiline, or derived from pyromelliticdianhydride, 4,4′-oxydianiline and paraphenylenediamine.
 11. The methodof claim 6, wherein the second polyamic acid is derived frompyromellitic dianhydride and 4,4′-oxydianiline, or derived from3,3′,4,4′-biphenyl tetracarboxylic dianhydride and paraphenylenediamine,or derived from pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine, or derived from 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, pyromellitic dianhydride, 4,4′-oxydianiline, or derivedfrom 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromelliticdianhydride, 4,4′-oxydianiline and paraphenylenediamine, or derived fromi) blocks of pyromellitic dianhydride and 4,4′-oxydianiline and ii)blocks of pyromellitic dianhydride and paraphenylenediamine, or derivedfrom pyromellitic dianhydride, oxydiphthalic dianhydride and1,3-bis-(4-aminophenoxy) benzene, or a mixture thereof.
 12. The methodof claim 9, wherein the submicron fumed metal oxide comprises fumedalumina, fumed silica or a mixture thereof.
 13. A method of reducing theamount of colorant in a multilayer film and achieving an L* color lessthan 30 and a 60 degree gloss value less than 10, the method comprising:a) providing a first polyamic acid solution containing a first polyamicacid for forming a first polyimide layer; b) providing a second polyamicacid solution containing a second polyamic acid, a first polyimideparticle matting agent, and a first submicron carbon black for forming asecond polyimide layer; c) providing a third polyamic acid solutioncontaining a third polyamic acid, a second polyimide particle mattingagent, and a second submicron carbon black for forming a third polyimidelayer; d) adding at least one first submicron fumed metal oxide to thesecond polyamic acid solution; e) adding at least one second submicronfumed metal oxide to the third polyamic acid solution; f) coextrudingthe first, second and third polyamic acid solutions, wherein the secondand third polyamic acid solutions are in direct contact with oppositesides of the first polyamic acid solution; and g) imidizing thecoextruded layers to form the first, second and third polyimide layers.14. The method of claim 13, wherein the first polyamic acid is derivedfrom pyromellitic dianhydride and 4,4′-oxydianiline, or derived frompyromellitic dianhydride, 4,4′-oxydianiline and paraphenylenediamine.15. The method of claim 13, wherein the second polyamic acid is derivedfrom pyromellitic dianhydride and 4,4′-oxydianiline, or derived from3,3′,4,4′-biphenyl tetracarboxylic dianhydride and paraphenylenediamine,or derived from pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine, or derived from 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, pyromellitic dianhydride, 4,4′-oxydianiline, or derivedfrom 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromelliticdianhydride, 4,4′-oxydianiline and paraphenylenediamine, or derived fromi) blocks of pyromellitic dianhydride and 4,4′-oxydianiline and ii)blocks of pyromellitic dianhydride and paraphenylenediamine, or derivedfrom pyromellitic dianhydride, oxydiphthalic dianhydride and1,3-bis-(4-aminophenoxy) benzene, or a mixture thereof.
 16. The methodof claim 13, wherein the third polyamic acid is derived frompyromellitic dianhydride and 4,4′-oxydianiline, or derived from3,3′,4,4′-biphenyl tetracarboxylic dianhydride and paraphenylenediamine,or derived from pyromellitic dianhydride, 4,4′-oxydianiline andparaphenylenediamine, or derived from 3,3′,4,4′-biphenyl tetracarboxylicdianhydride, pyromellitic dianhydride, 4,4′-oxydianiline, or derivedfrom 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, pyromelliticdianhydride, 4,4′-oxydianiline and paraphenylenediamine, or derived fromi) blocks of pyromellitic dianhydride and 4,4′-oxydianiline and ii)blocks of pyromellitic dianhydride and paraphenylenediamine, or derivedfrom pyromellitic dianhydride, oxydiphthalic dianhydride and1,3-bis-(4-aminophenoxy) benzene, or a mixture thereof.
 17. The methodof claim 13, wherein the first submicron fumed metal oxide comprisesfumed alumina, fumed silica or a mixture thereof.
 18. The method ofclaim 13, wherein the second submicron fumed metal oxide comprises fumedalumina, fumed silica or a mixture thereof.
 19. The method of claim 13,wherein the second and third polyimide layers are the same.